At 06:28 PM 1/7/2003 -0800, you wrote: >Hi Hakan, >I live in California but we're building this place for someone else in >eastern Montana- near Canada, and extremely cold in winter and extremely >hot (115-120 F!!!!!!!!) in summer.
Ok, but the sun is more comparable to southern Europe since it is more or less the same level. In Sweden for example, the sun have very much lower angle and the largest cooling needs are in April - May. The air temperatures are still very low, but the low angle of the sun creates some substantial over heating problems in our office buildings. In fact the cooling equipments have to be larger in Sweden than corresponding buildings in Spain in August, which is their warmest month. >Let me explain again what I meant about our heating and cooling strategy, >as I think you and I are using different terms (what you called passive >solar panels I would call active solar for instance). Also I think that >some people new to building energy efficiency might be confused by active >versus passive heating, so I want to clarify again. Yes, you are right, for me is passive solar panels typically heating of water etc. and active is generating electricity. >Passive solar very simple and is commonly done for heating (it might not >provide all the heating in their winters unless designed extremely well, >but it will help a lot). It is done using southfacing windows (and by >minimising north and west windows altogether, and by orienting a house so >that the long side faces south in this hemisphere, north in the southern >hemisphere of course). > In the winter when there is a low sun angle, the sunlight can penetrate >far into a home, sunlight will land on a dark concrete or stone or adobe >(earth/stone) floor in this home or on some other storage medium such as a >concrete or adobe or cob wall, and the floor (or other storage medium), >being a dark color, turns the light energy into heat energy. Good >insulation keeps that heat in. The storage medium absorbs heat energy and >releases it slowly throughout the night. This is obviously a very >simplistic explanation but it is old and very proven technology, extremely >common. People do it successfully in the same area as where we will be >building. It is kept from overheating in summer by the fact that in the >summer the sun angle is high, so if your roof has a large enough overhang >(which is convenient since you need large overhangs to protect strawbale >walls) the overhang keeps the sun from penetrating into the house and >heating the thermal mass. The thermal mass also helps moderate summertime >heat by acting as a flywheel- it cools at night, and absorbs some of the >heat of the day. I realized that it was a solar design for warmer climates, but I did not see it in the beginning. It was first after you told me that I was wrong, that I saw it. >Obviously the spanish and middle eastern people and >Southwestern US indians and many others in hot climates had many strategies >to do this kind of cooling, not sure who did heating that way (passive >heating is easier if you have access to cheap glass) There are other >natural and passive ways to cool a hot home but in our experience being in >the existing strawbale house at the community center in Montana, the >insulation of it alone was enough to keep it somewhat reasonable in the >extreme heat. I agree with you. >Active solar is where you have a panel on your roof or on the south side of >your house that is used to heat air. The hot air is used to heat a thermal >mass (such as some rocks, inside some insulated structure). The thermal >mass then releases the heat slowly into the house when it's needed at >night, often via some mechanical heat transfer system (a fan moving the >house air over the rocks to heat it, then piping it into the home). I have some experiences from those systems and it is some serious problems with it, some has to do with growing of organisms etc. They were popular in Sweden for a while, but are in less use today. Air is also a quite inefficient transport media. Through simulations, we have proved many times that using the buildings structure are much more efficient and less problems. >The kind of work you're talking about doing in 1973 probably laid the >foundation for modern efficient building science- thank you. I like to think that it brought back some common sense and proved why all those traditional designs worked so well. If you are talking of the most common building practises of today, except for Sweden, I am not sure that I want to be identified with them. I like to be identified with the common building science that is going to be used in 20 to 30 years. Today it is a mess. > Window quilts are an overlooked aspect of insulation- I knew someone who >made them with Mylar inside, and it improved their efficiency at keeping >heat in or out... That is a sample of working with the emission, which only indirectly influences the air temperature. We humans are more sensitive to effects of emission than the air temperature. You can read more about it on our site. >Mark > >At 02:37 AM 1/8/2003 +0100, you wrote: > >At 04:12 PM 1/7/2003 -0800, you wrote: > > >Hakan, thanks, > > > > > > >Passive solar design assumes that you have energy capture and internal > > mass > > > >for to store it. A straw bale house might have too good insulation to be > > > >fully compatible with most of those principles and benefit probably more > > > >from internal heat sources like lights, people etc.. The trade off > between > > > >capture/storage and the lessening of efficiency in insulation/emission > > > >factors for that, might be negative for a straw bale house. > > > > > >This is wrong, unfortunately. Passive solar is completely compatible with > > >superinsulation strategies, with the thick walls and deep window wells of > > >strawbale, and the adobe floor acts as thermal mass. > > > >The decade after 1973, we did many simulation projects for experiment > >buildings and also evaluation follow up. In this was a number of super > >insulation projects and some of them with very low infiltration (air > >movement through the construction) in combination with very low > >ventilation. The radiation from the sun and its angle is key. Yes, I am > >wrong if your main goal is to keep the house cool with passive solar design. > >Since we talked about heating, I assumed that you looked for energy > >to warm the house, my mistake. Of course, your solar design's main goal > >in the area you live, must be to keep the house cool in the summer. > > > >I now live in the Barcelona area (Southern Europe), which is at the same > >level as Boston as far as the sun concerns. Here, your description is a > >passive solar design with the aim to keep the house cool during the warm > >half year. Super insulation keep it warm during the winter, but unless you > >do not capture the sun by solar panels, you will not get much of heating > >addition. The benefit is that you can get a lot of heat in the winter with > >passive solar panels. You are also right in that super insulation is not > >a contradiction in keeping the house cool in the summer, it rather helps > >if you really keep the sun out. > > > >Of course you will get some addition in winter when the sun is lower and > >maybe you should try to enhance that. In Spain/Italy the traditional system > >was/is outside covers for the windows. In summer they are closed > >during the day, to keep the sun out and open during the night to cool the > >house down. In winter it is the opposite closed during the night and open > >during the day to get some heat from the sun. I guess that you have this > >in your area also, from the Spanish influence. Those covers can today > >be improved to be a part of the insulation and maybe this is a low cost > >route to follow. > > > > > > > > > >Yahoo! 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